In the cheese production process, in a known manner, curd is prepared from milk in a curd maker. Usually, the curd in the curd maker is stirred and cut and the whey thereby released is partly discharged and for the rest is supplied together with the curd mass via a buffer tank to an apparatus for producing blocks of cheese. Although cheese can be prepared from curd in many ways, in large-scale cheese production often use is made of so-called draining or forming columns. In the processing of pre-acidified curd, e.g. in the production of Cheddar-type cheese, forming columns (also called block formers) are used where pre-drained and acidified and salted curd is processed. Draining columns are used in the processing of a whey-curd mixture shortly after curd making. Both types of columns comprise a hollow vertical tube placed on a support, to which, in operation, at the top, a mixture of curd and whey is supplied in the case of draining columns, or the acidified and pre-drained but still whey-containing curd in the case of forming columns. In such a column, the curd is increasingly compacted from the top down, so that at the bottom of the column curd blocks can be cut off. To this end, at the bottom of the column, a horizontally acting guillotine knife is placed. The guillotine knife closes off the column and in the closed position supports the curd column. The guillotine knife is periodically opened, so that the curd column in the tube can move down over a settable distance. To this end, a dosing plate vertically reciprocable in a sliding sleeve (in case of draining columns) or dosing chamber (in case of forming columns) is present, which is placed under the guillotine knife. Prior to opening of the guillotine knife the dosing plate is moved to a position just below the guillotine knife, taking over the support of the curd column when the guillotine knife is opened. Thereupon the dosing plate is moved down over a settable distance, which corresponds to the desired height of the curd block. When thereupon the guillotine knife is moved into the closing position again, a curd block is thereby cut off from the curd column and the knife in turn takes over the curd column supporting function from the dosing plate.
The cut-off curd block now lies on the dosing plate in the sliding sleeve, or dosing chamber. The dosing plate is then moved further down until the curd block is at the bottom of the sliding sleeve or dosing chamber. Then, in the case of draining columns the sliding sleeve with the curd block therein is moved sideways to a position above a cheese mold and transferred into the cheese mold. In the case of forming columns, the cut-off curd block is moved out sideways with the aid of one of the sidewalls via an opposite sidewall which can be swung clear or removed, and is externally moved to a filling installation.
The guillotine knife has a front end and a rear end and two longitudinal edges. The front end forms a cutting edge, while the rear end is connected with drive means, which can comprise, for example, a pneumatic cylinder, and which can cause the guillotine knife to move back and forth between the open position and the closed position. The two longitudinal edges are in the guiding slots of guiding means. The guiding means typically comprise two elongate guiding blocks of a suitable plastic such as, for example, polyethylene of the UHMWP (Ultra High Molecular Weight Polyethylene) type, or other suitable plastic. The guiding blocks are usually fixedly mounted in and/or between stainless steel frame parts under the vertical tubular column and are provided with the guiding slots mentioned, in which the longitudinal edges of the guillotine knife are guided.
The known guiding means hence comprise plastic guiding blocks, which are mounted on stainless steel frame parts. Since plastic materials and stainless steel have different thermal expansion coefficients, slits may be formed between mutually abutting surfaces of these different materials, which are difficult to clean and during use constitute a potential source of infection by accumulation of product residues. Also, via such slits, leakage can arise. In block formers, use is made of air pressure differences between on the one hand the interior of the vertical tubular column and the dosing chamber and on the other hand the environment, as well as of air pressure differences between the interior of the column and the interior of the dosing chamber. Leakage via slits between plastic guiding blocks and stainless steel frame parts is therefore undesired.